1. Technical Field
The present disclosure relates to an annular optical spacer. More particularly, the present disclosure relates to an annular optical spacer with protruding structures.
2. Description of Related Art
Due to the popularity of personal electronic products and mobile communication products having camera functionalities, such as smart phones and tablet personal computers, the demand for compact optical systems has been increasing. The compact optical systems have gradually evolved toward the field of higher megapixels, and have to satisfy the requirements of lightweight and high image quality.
A compact optical system generally includes a plurality of lenses and at least one optical spacer. The optical spacer is disposed between two adjacent lenses for controlling a separation distance between the two lenses, so that damages caused by scraping and colliding between the two lenses can be avoided.
FIG. 1A is a front schematic view of a conventional optical spacer 10. FIG. 1B is a partially enlarged cross-sectional view taken along line 1b-1b of the optical spacer 10 in FIG. 1A. In FIG. 1A, the optical spacer 10 has a smooth surface 11. As shown in FIG. 1B, when an incident light M1 strikes the surface 11, a reflected light R1 is formed complying with the law of reflection. A diffuse reflection hardly occurs due to the smoothness of the surface 11, and the reflected light R1 tends to enter into the optical effective region so as the form an unexpected light. When the number of the unexpected lights is excessive, the image quality is poor and thereby cannot satisfy the requirements of high-end optical systems with camera functionalities.